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Low work-function, mechanically and thermally robust emitter for thermionic energy converters

a thermionic energy converter and low work function technology, applied in the direction of thermal electric motors, electrical devices, electrical discharge tubes, etc., can solve the problems of inability to reduce the work function of silicon carbide, inability to achieve the work function of tec electrodes, and inability to achieve the work function of sic, etc., to achieve the effect of stable operation

Inactive Publication Date: 2017-03-28
THE BOARD OF TRUSTEES OF THE LELAND STANFORD JUNIOR UNIV
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Benefits of technology

The patent describes an improved support structure for a thermionic energy converter that is mechanically stable and has a stable surface coating for efficient thermionic emission. The support structure is made of silicon carbide and includes support members with U-shaped cross sections to provide stiff suspension legs of SiC. This structure prevents undesirable contact between the emitter and substrate during heating and maintains efficient thermionic energy converter operation at high temperatures. The patent provides a solution for the needs of low work-function, mechanically and thermally robust emitter for thermionic energy converters.

Problems solved by technology

However, silicon carbide has a work function that is undesirably large for TEC electrode applications.
A straightforward attempt to reduce the SiC work function (e.g., by coating with Barium) tends to fail because of lack of adhesion of the Ba coating to SiC.

Method used

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  • Low work-function, mechanically and thermally robust emitter for thermionic energy converters
  • Low work-function, mechanically and thermally robust emitter for thermionic energy converters
  • Low work-function, mechanically and thermally robust emitter for thermionic energy converters

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Experimental program
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Embodiment Construction

[0028]In this description, several experiments relating to the above-described principles are described. Section I relates to fabrication, section II provides the experimental results, and section III give the conclusions.

I. Fabrication

A. Mechanically Robust Suspended Micro-Emitters

[0029]The emitter was configured as a silicon carbide (SiC) center pad 304 suspended above the substrate using four SiC crab-leg beams 306 as shown on FIGS. 3A-B. Here 302 are the support posts and 308 are holes in the center pad 304 to facilitate the undercut etch to form the suspended structure. This design accommodates thermal expansion of the order of 1% that occurs at the typical operating temperatures of 1000° C.-2500° C. It also provides a high thermal resistance between center pad 304 and support posts 302, which is important. We used a conformal sidewall deposition of poly-SiC to form stiff suspension legs with U-shaped cross sections, which increases the out-of-plane rigidity and avoids contact ...

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PUM

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Abstract

Improved thermionic energy converters are provided by electrodes that include a silicon carbide support structure, a tungsten adhesion layer disposed on the silicon carbide support structure, and an activation layer disposed on the tungsten adhesion layer. The activation layer is a material that lowers the electrode work function, such as BaO, SrO and / or CaO.

Description

CROSS REFERENCE TO RELATED APPLICATIONS[0001]This application claims the benefit of U.S. provisional patent application 61 / 877,247, filed on Sep. 12, 2013, and hereby incorporated by reference in its entirety.GOVERNMENT SPONSORSHIP[0002]This invention was made with Government support under contract number W91CRB-10-1-0001 awarded by the Department of the Army. The Government has certain rights in this invention.FIELD OF THE INVENTION[0003]This invention relates to thermionic energy conversion.BACKGROUND[0004]Thermionic energy converters (TECs) are heat engines that convert heat directly to electricity at very high temperatures, typically >1000° C. Electrons are thermionically emitted from a hot emitter and collected at a relatively cool collector, effectively playing the role of the working fluid. FIG. 1A shows the basic configuration for this effect. An emitter electrode 102 is heated (shown schematically by arrows 108). Electrons 110 emitted by emitter electrode 102 are collect...

Claims

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Application Information

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IPC IPC(8): H02N10/00H01J45/00
CPCH01J45/00
Inventor LEE, JAE HYUNGBARGATIN, IGORVANCIL, BERNARDHOWE, ROGER T.
Owner THE BOARD OF TRUSTEES OF THE LELAND STANFORD JUNIOR UNIV